Unless otherwise indicated, the foregoing is not admitted to be prior art to the claims recited herein and should not be construed as such.
Switching power supplies, such as buck converters, boost converters, etc., may operation in pulse width modulation (PWM) mode. The output voltage can be regulated by varying the duty cycle or pulse width of a pulsed control signal. Switching efficiency, however, drops off at lower loads. Due to an increasing range of functionality provided in mobile computing devices (e.g., communication devices, computer tablets, etc.), low load conditions are becoming more common. Accordingly, switching using PWM mode only becomes increasingly less efficient.
Switching power supply designs may include a pulse frequency modulation (PFM) mode of operation, sometimes referred to as “power saving mode.” Switching power supplies may operate in PFM mode to support certain functionality in a power management circuit when it is in a low power mode. In PFM mode, the frequency of the control pulses varies with load current and switching cycles are initiated only as needed to maintain the output voltage. The ability of the switching power supply to provide current in PFM mode is typically based on a preset PFM current limit value to improve efficiency under low load conditions. Increasing the current limit allows PFM mode to provide more power under low loads, but at the expense of increasing ripple artifacts in the output voltage.